How to use sprite groups in pygame

Question

So I've gotten to the point in my program where I need to create a group for some sprites that the player can collide with without dying (like some other sprites I may have on screen).

I've scoured Google but it appears that the official pygame documentation is useless and/or hard to comprehend. I'm looking for just a wee bit of help from anyone who knows a bit about this.

First, I need to find out how to create a group. Does it go in the initial game setup?

Then adding a sprite to a group upon its creation. The pygame site has this to say on the subject:

Sprite.add(*groups)

So... how does one use this? Let's say I have an sprite named gem. I need to add gem to the gems group. Is it:

gem = Sprite.add(gems)

I doubt it, but without any examples to go off of on the site, I am at a loss.

Furthermore, I would love to be able to edit attributes for a certain group. Is this done by defining a group like I would a class? Or is it something I define within the definition for the existing sprite, but with an 'if sprite in group'?

Answer 1

To answer your first question; to create a group you would do something like this:

gems = pygame.sprite.Group()

Then to add a sprite:

gems.add(gem)

Regarding the attributes for the group you'd like to edit it depends what they are. For example you could define something like this to indicate the direction of the group:

gems.direction = 'up'

Answer 2

I know this question has already been answered, but the best method is like what kelwinfc suggested. I'll elaborate so it's more understandable.

# First, create you group
gems = pygame.sprite.Group()

class Jewel (pygame.sprite.Sprite): # Inherit from the Sprite
    def __init__ (self, *args): # Call the constructor with whatever arguments...
        # This next part is key. You call the super constructor, and pass in the 
        # group you've created and it is automatically added to the group every 
        # time you create an instance of this class
        pygame.sprite.Sprite.__init__(self, gems) 

        # rest of class stuff after this.

>>> ruby = Jewel()  
>>> diamond = Jewel()  
>>> coal = Jewel()

# All three are now in the group gems. 
>>> gems.sprites()
[<Jewel sprite(in 1 groups)>, <Jewel sprite(in 1 groups)>, <Jewel sprite(in 1 groups)>]

You can also add more with gems.add(some_sprite) and likewise remove them with gems.remove(some_sprite).